fission

noun
fis·​sion | \ ˈfi-shᵊn How to pronounce fission (audio) , -zhᵊn \

Definition of fission

 (Entry 1 of 2)

1 : a splitting or breaking up into parts
2 : reproduction by spontaneous division of the body into two or more parts each of which grows into a complete organism
3 : the splitting of an atomic nucleus resulting in the release of large amounts of energy

fission

verb
fissioned; fissioning; fissions

Definition of fission (Entry 2 of 2)

intransitive verb

: to undergo fission

transitive verb

: to cause to undergo fission

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Other Words from fission

Noun

fissional \ ˈfi-​shə-​nəl How to pronounce fissional (audio) , -​zhə-​ \ adjective

Examples of fission in a Sentence

Recent Examples on the Web: Noun The primary fission stage is a low-yield nuclear weapon that then triggers the secondary stage, which sets off a much, much larger fusion explosion. Kyle Mizokami, Popular Mechanics, "What Is Trump’s New Nuclear Weapon?," 10 Sep. 2020 In fact, Einstein had signed a 1939 letter written by two other physicists warning President Franklin D. Roosevelt that Germany was experimenting with nuclear fission, according to Oristano. Manuel Mendoza, Dallas News, "What if? New work by Dallas playwright Mark Oristano rewrites history," 10 Sep. 2020 A week after German scientists discovered nuclear fission in 1938, a physicist at Berkeley drew a crude bomb on his blackboard. Marty Judge Community Voices Contributor, San Diego Union-Tribune, "Commentary: The U.S. quest for nuclear control has been a rocky road. Here’s what would make it smoother.," 7 Sep. 2020 The control rods—which can encase the fuel rods, blocking neutrons and halting the fission chain reaction—are actively held in place above the fuel rods by a motor. Scott K. Johnson, Ars Technica, "NuScale’s small nuclear reactor is first to get US safety approval," 1 Sep. 2020 Supporters anticipate a renaissance in fission that could draw $5.9 trillion in global investment through 2050. Will Wade, Bloomberg.com, "Mini-Reactors Are Gaining Traction in the Push for Greener Grids," 31 Aug. 2020 Cs-134, Cs-137 & Ru-103 associated w/Nuclear fission @ higher[ ] than usual levels (but not harmful for human health). Kyle Mizokami, Popular Mechanics, "Radiation Leak in Europe Points to a Possible Russian Weapons Test," 29 June 2020 The development cycle for nuclear fusion technology can seem long, especially compared to the iterative improvement of fission reactors—the ones in all of our nuclear power plants today. Caroline Delbert, Popular Mechanics, "For Better Fusion Reactors, We Must Stop the Blobs," 1 June 2020 These results are harder to interpret, however, because physicists do not know exactly how many neutrinos should be produced in fission reactors. William Charles Louis, Scientific American, "Hidden Neutrino Particles May Be a Link to the Dark Sector," 1 July 2020 Recent Examples on the Web: Verb The point is that by analyzing the array of radioactive fission products – those that can be captured and analyzed – nuclear forensic specialists can start to figure out if the atoms that fissioned were U-235, Pu-239, or (in some cases) U-238. Andrew Karam, Popular Mechanics, "Nuclear Forensics: How Scientists Can Tell Whether North Korea Is Lying About Its Bomb Test," 7 Jan. 2016 Anyone can see that fissioning uranium 235 or plutonium can be used to generate electricity. Scientific American, "Readers Respond to the January 2018 Issue," 1 Jan. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'fission.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of fission

Noun

circa 1617, in the meaning defined at sense 1

Verb

1929, in the meaning defined at intransitive sense

History and Etymology for fission

Noun

borrowed from Latin fissiōn-, fissiō, from fid-, variant stem of findere "to split, cleave" + -tiōn-, -tiō, suffix of verbal action — more at bite entry 1

Verb

derivative of fission entry 1

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Time Traveler for fission

Time Traveler

The first known use of fission was circa 1617

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Statistics for fission

Last Updated

18 Sep 2020

Cite this Entry

“Fission.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/fission. Accessed 20 Oct. 2020.

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More Definitions for fission

fission

noun
How to pronounce fission (audio)

English Language Learners Definition of fission

physics : a process in which the nucleus of a heavy atom is split apart
biology : a kind of reproduction in which a cell or body divides into two or more parts and each part grows into a whole new individual

fission

noun
fis·​sion | \ ˈfi-shən How to pronounce fission (audio) \

Kids Definition of fission

1 : a method of reproduction in which a living cell or body divides into two or more parts each of which grows into a whole new individual
2 : the process of splitting an atomic nucleus with the release of large amounts of energy

fission

noun
fis·​sion | \ ˈfish-ən also ˈfizh- How to pronounce fission (audio) \

Medical Definition of fission

1 : a method of reproduction in which a living cell or body divides into two or more parts each of which grows into a whole new individual
b : the splitting of an atomic nucleus resulting in the release of large amounts of energy

called also nuclear fission

Other Words from fission

fission verb fissioned; fissioning\ ˈfish-​(ə-​)niŋ also ˈfizh-​ How to pronounce fissioning (audio) \
fissional \ ˈfish-​ən-​ᵊl also ˈfizh-​ How to pronounce fissional (audio) \ adjective

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More from Merriam-Webster on fission

Nglish: Translation of fission for Spanish Speakers

Britannica English: Translation of fission for Arabic Speakers

Britannica.com: Encyclopedia article about fission

Comments on fission

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